2. Scientific MeasurementsScientific Measurements  SI Units  Significant Figures

3. SI UnitsSI Units  Measurement system universal to scientists.  Measurement standards (base and derived)  Base unit—  Quantity we can MEASURE  Derived unit--  Quantity provided by CALCULATION

4. SI Units (cont.)SI Units (cont.) Base  Mass = kilogram (kg)  Length = Meter (m)  Time = Second (s)  Temperature = Kelvin (°K) Derived  Volume = m 3, we will use cm 3 /ml  ml is NOT an SI unit  Density = kg/m 3, we will use g/cm 3 or g/ml

5. Mass vs. WeightMass vs. Weight  What is the difference?  How do we measure mass?

6. Density  Physical property of matter/substances  Used for substance identification  Provides information on how solids/liquids interact  Ratio of a substance’s mass and volume  Density = Mass/Volume  Units = SI Unit (kg/m 3 ), we will use g/cm 3 or g/ml

7. Example 1 : A student obtains a mass of 5.03 g for a metal and a volume of 3.24 ml?

8. Example 2: What is the volume of a substance with a density of 0.824 g/ml and a mass of 0.451g?

9. Example 3: A student records V1= 2.7ml and V2= 3.4 ml after placing an object in a graduated cylinder. The mass of an empty beaker is 1.13g and the mass of both the beaker and substance is 4.13g. What is the object’s density? Example 3: A student records V1= 2.7ml and V2= 3.4 ml after placing an object in a graduated cylinder. The mass of an empty beaker is 1.13g and the mass of both the beaker and substance is 4.13g. What is the object’s density?

10. Density ProblemsDensity Problems 1) An object has a mass of 4 grams and a volume of 1.7 cm 3. What is it’s density? 2) What is an object’s mass if it’s density is 8.3 g/cm 3 and the volume is 4 cm 3 ? 3) What is the volume of an object with a mass of 11 grams and a density of 4.2 g/cm 3 ? 4) An object’s mass is found to be 40 grams. When this object is placed in a graduated cylinder with a V1 of 17ml, the V2 becomes 20 ml. What is the object’s density?

11. Homework  Density Problems